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Intestinal mucin, a family of glycoproteins secreted by goblet cells, is the main constituent of the mucus protecting the gastrointestinal tract. For optimal mucosal protection, both the quantitative and qualitative characteristics of mucin are essential. To evaluate how viscosity influences ileal apparent digestibility and mucin biology, a highly viscous nonfermentable soluble polysaccharide, carboxymethylcellulose (CMC), was fed to weaned piglets for 15 d. The ileal crude mucin concentration was determined by ethanol precipitation, and changes in goblet cell subtypes were analyzed by the histochemistry of ileal and colonic tissues. As expected, CMC increased the viscosity of ileal digesta and the moisture of feces (P < 0.001). The crude mucin concentration and output at the ileum were higher (P < 0.05) in pigs fed CMC than those fed the control diet. Increasing intestinal content viscosity in pigs fed CMC had no significant effects on the ileal apparent digestibility of dry matter, organic matter, nitrogen, and minerals. The number of total ileal goblet cells per villus also was higher (+30%, P < 0.05) in pigs fed the CMC diet compared with controls. This increase was essentially accounted for by increased numbers of acidic and acidic sulfated mucin-containing cells (+30%, P < 0.05). Trends (P = 0.06) toward decreased numbers of neutral and acidic mucin-containing cells in ileal crypts were also noted. In conclusion, increasing intestinal content viscosity in weaned piglets fed CMC increased the ileal mucin output and numbers and maturation of goblet cells in ileal villi without effects on the apparent digestibility of the diet. KEY WORDS: * viscosity * intestine * piglet * goblet cells * mucin

Feeding legume grains to pigs usually increases losses of endogenous proteins at the terminal ileum. However, the identity of such proteins is largely unknown. This study was undertaken to determine the ileal flow and identity of soluble proteins present in large concentrations in ileal digesta of young pigs fed soybean meal (SBM), peas (P), faba beans (FB), or blue lupin (L) in expt. 1, and white (WPC) or black (BPC) chickpeas in expt. 2. Protein in the control diet (C) was provided by casein. Ileal digesta proteins were analyzed using sodium dodecyl sulfate polyacrylamide gel electrophoresis, Coomassie blue staining, densitometry and N-terminal amino acid sequencing. Three protein bands at molecular masses of 25, 27, and 30 kDa had a higher ileal flow (P < 0.05) in the pigs fed the legume-based diets compared to those fed the control diet in expt. 2. This was true for the 25- and 30-kDa proteins (P < 0.05) and the 27-kDa protein (P < 0.10) in pigs fed the legume-containing diets in expt. 1. These proteins shared N-terminal amino acid sequences with enzymes of the serine protease family including pig trypsin (25 kDa) and blood coagulation factor IX or chymotrypsin (27 and 30 kDa). KEY WORDS: * piglets * endogenous proteins * serine-protease * proteins * densitometry * sequence analysis